A disk drive comprises a rotating disk and a head over the disk to magnetically write to and read data from the disk. The head may be connected to a distal end of an actuator arm that is rotated about a pivot to position the head radially over the disk. During write/read operations, the head flies above the disk surface on a cushion of air formed by the rotating disk. The fly height of the head may be adjusted by a dynamic fly height (DFH) heater or other mechanism. When the head touches down on the rotating disk, the head and/or disk may be damaged. Therefore, it is desirable to detect touchdown of the head on the disk and to stop the detected touchdown to prevent damage to the head and/or disk.